Netty5实现客户端和服务端

知识点

一个thread + 队列 == 一个单线程线程池   =====> 线程安全的，任务是线性串行执行的

线程安全，不会产生阻塞效应 ，使用对象组

线程不安全，会产生阻塞效应， 使用对象池

Netty5服务端接受客户端的消息，需要继承SimpleChannelInboundHandler类，同理，客户端接受服务端消息，也需要实现该类

针对单客户端多连，断开重连，可以看第五点

1、Netty5Server.java

package com.example.netty.lesson6;

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.*;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;

/**
 * @author yangwj
 * @date 2020/4/4 21:29
 */
public class Netty5Server {
    public static void main(String[] args) {
        //服务类
        ServerBootstrap bootstrap = new ServerBootstrap();
        //boss worker----其实就是线程池
        EventLoopGroup boss = new NioEventLoopGroup();
        EventLoopGroup worker = new NioEventLoopGroup();
        try {
            //设置线程池
            bootstrap.group(boss,worker);

            //设置socket工厂
            bootstrap.channel(NioServerSocketChannel.class);

            //设置管道工厂
            bootstrap.childHandler(new ChannelInitializer<Channel>() {
                @Override
                protected void initChannel(Channel channel) throws Exception {
                    channel.pipeline().addLast(new StringDecoder());
                    channel.pipeline().addLast(new StringEncoder());
                    channel.pipeline().addLast(new ServerHandler());
                }
            });
            //设置参数
            bootstrap.option(ChannelOption.SO_BACKLOG,2048);//表示可以接受2048连接(连接缓冲池设置)
            bootstrap.childOption(ChannelOption.SO_KEEPALIVE,true);//维持连接的活跃，清除死连接
            bootstrap.childOption(ChannelOption.TCP_NODELAY,true);//关闭延迟发送
            //绑定端口
            ChannelFuture future = bootstrap.bind(51503);
            //等待服务端关闭
            future.channel().closeFuture().sync();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }finally {
            //释放资源
            boss.shutdownGracefully();
            worker.shutdownGracefully();
        }
    }
}

2、ServerHandler.java

package com.example.netty.lesson6;

import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;

/**
 * @author yangwj
 * @date 2020/4/4 21:41
 */
public class ServerHandler extends SimpleChannelInboundHandler<String> {
    @Override
    protected void messageReceived(ChannelHandlerContext ctx, String msg) throws Exception {
        System.out.println("接受的消息："+msg);

        //返回给客户端信息
        ctx.channel().writeAndFlush("服务端返回给你：你好");
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        System.out.println("exceptionCaught");
    }

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        //连接时触发
        System.out.println("channelActive");
    }

    @Override
    public void channelInactive(ChannelHandlerContext ctx) throws Exception {
        //断开时触发
        System.out.println("channelInactive");
    }
}

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3、Netty5Client.java

package com.example.netty.lesson6;

import io.netty.bootstrap.Bootstrap;
import io.netty.channel.Channel;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

/**
 * @author yangwj
 * @date 2020/4/4 21:59
 */
public class Netty5Client {
    public static void main(String[] args) {
        //服务类
        Bootstrap bootstrap = new Bootstrap();

        //woker
        EventLoopGroup worker = new NioEventLoopGroup();
        try {
        //设置线程池
        bootstrap.group(worker);

        //设置socket工厂
        bootstrap.channel(NioSocketChannel.class);

        //设置管道
        bootstrap.handler(new ChannelInitializer<Channel>() {
            @Override
            protected void initChannel(Channel channel) throws Exception {
                channel.pipeline().addLast(new StringDecoder());
                channel.pipeline().addLast(new StringEncoder());
                channel.pipeline().addLast(new ClientHandler());
            }
        });
        //连接服务端
        ChannelFuture connect = bootstrap.connect("127.0.0.1",51503);
        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
        while (true){
                System.out.println("请输入：");
                String msg = null;

                msg = bufferedReader.readLine();
                connect.channel().writeAndFlush(msg);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            worker.shutdownGracefully();
        }
    }
}

4、ClientHandler.java

package com.example.netty.lesson6;

import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;

/**
 * @author yangwj
 * @date 2020/4/4 22:08
 */
public class ClientHandler extends SimpleChannelInboundHandler<String> {
    @Override
    protected void messageReceived(ChannelHandlerContext channelHandlerContext, String msg) throws Exception {
        System.out.println("客户端收到的消息："+msg);
    }
}

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##########以上存在连接断开，无法重连的问题，下面是解决方案#############

5、Netty5MutilClient.java

package com.example.netty.lesson6;

import io.netty.bootstrap.Bootstrap;
import io.netty.channel.Channel;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.atomic.AtomicInteger;

/**
 * @author yangwj
 * @date 2020/4/4 22:33
 */
public class Netty5MutilClient {
    //服务类
    private Bootstrap bootstrap = new Bootstrap();
    //会话
    private List<Channel> channels = new ArrayList<>();
    //引用计数器
    private final AtomicInteger index = new AtomicInteger();
    //初始化
    public void init(int count){
        EventLoopGroup worker = new NioEventLoopGroup();
        //设置线程池
        bootstrap.group(worker);

        //设置socket工厂
        bootstrap.channel(NioSocketChannel.class);

        //设置管道
        bootstrap.handler(new ChannelInitializer<Channel>() {
            @Override
            protected void initChannel(Channel channel) throws Exception {
                channel.pipeline().addLast(new StringDecoder());
                channel.pipeline().addLast(new StringEncoder());
                channel.pipeline().addLast(new ClientHandler());
            }
        });
        for (int i =1; i<count; i++){
            //连接服务端
            ChannelFuture connect = bootstrap.connect("127.0.0.1",51503);
            channels.add(connect.channel());
        }

    }

    /**
     * 获取会话
     * @return
     */
    public Channel nextChannel(){
        return getFirstActiveChannel(0);
    }

    private Channel getFirstActiveChannel(int count){
        Channel channel = channels.get(Math.abs(index.getAndIncrement() % channels.size()));
        if(!channel.isActive()){
            //重连
            reconnect(channel);
            if(count >= channels.size()){
                throw new RuntimeException("no can use channel");
            }
            return getFirstActiveChannel(count + 1);
        }
        return channel;

    }

    /**
     * 重连
     * @param channel
     */
    private void reconnect(Channel channel){
        synchronized(channel){
            if(channels.indexOf(channel) == -1){
                return ;
            }
            Channel newChannel = bootstrap.connect("127.0.0.1", 51503).channel();
            channels.set(channels.indexOf(channel), newChannel);
        }
    }
}

6、启动客户端Netty5MutilClientStart.java

package com.example.netty.lesson6;

import java.io.BufferedReader;
import java.io.InputStreamReader;

/**
 * 单客户端多连接
 * @author yangwj
 * @date 2020/4/4 22:49
 */
public class Netty5MutilClientStart {
    public static void main(String[] args) {
        Netty5MutilClient client = new Netty5MutilClient();

        client.init(5);

        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
        while (true){
            try {
                System.out.println("请输入：");
                String msg = bufferedReader.readLine();
                client.nextChannel().writeAndFlush(msg);
            }catch (Exception e){
                e.printStackTrace();
            }
        }
    }
}

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完毕！